The aim of this study was to determine the effects of dietary supplementation with a combination of fish oil, bilberry extract, and lutein on subjective symptoms of asthenopia in humans by a double- blind, randomized, parallel-group, and placebo-controlled trial.

In the Placebo group, nine subjects ingested placebo capsules. Before and after supplementation, subjects completed a questionnaire to determine their asthenopia symptoms and were also assessed for mental fatigue symptom by the visual analog scale (VAS) test.

Asthenopia symptoms such as "stiff shoulder, low back pain", "frustration", "dry-eye", and "stuffy head" were improved in the Active group. Furthermore, a score of mental fatigue was improved after 4 weeks of supplementation, and no side effects were observed after the 4-week supplementation and a 2-week washout period in the Active group.

These results suggest that dietary supplementation with the combination of omega-3 fatty acid-rich fish oil, bilberry extract, and lutein may safely improve subjective symptoms of asthenopia and mental fatigue in humans.